Extraction of copper from molten metal melts



United States Patent 3,441,404 EXTRACTION OF COPPER FROM MOLTEN METAL MELTS Kenneth H. Ivey, Adelphi, Md., and Sidney J. Chastain, Knoxville, Tenn., assignors to the United States of America as represented by the Secretary of the Interior No Drawing. Filed Nov. 25, 1966, Ser. No. 597,162

Int. Cl. C22b 15/00 US. Cl. 75-76 Claims ABSTRACT OF THE DISCLOSURE Removing copper from molten scrap iron by adding sulfur and halide-containing compound to the melt whereby resultant halide vapor strips off copper-sulfur compound.

This invention relates to the removal of copper in the reclamation of metal scrap.

For some years now, the United States has imported large quantities of iron ore since foreign ore possesses higher quality than domestic ore and can be delivered at competitive costs. While there are large domestic supplies of scrap iron available in junk cars, it is considered unusable as clean basic cast iron because copper, in the form of small wires and tubing, is not removed by the junk dealer for economic reasons. When this scrap is melted, the ingot contains enough copper to cause the metal to be unusable as a source material for metallurgical industries.

It has now been discovered that copper can be removed from such metals by treating it in a molten state with sulfur and a halide-containing compound selected from the group consisting of alkali earth metal halides, alkali metal halides, alkali earth metal silicohalides, alkali metal silicohalides, KMgF KAlF KgTiFe, KgZI'F and K SnF One theory advanced with regard to the process is that the sulfur forms copper sulphide with copper in the metal, and the halide vaporizes and strips ofi the sulphide.

Therefore, it is an object of this invention to provide a method for the removal of copper from metal melts.

Another object is to provide cast iron and other metals free of copper.

A further object is the introduction of materials having a low vapor pressure into a bath of molten metal whereby the danger of explosion is eliminated.

A stil further object is the introduction of a volatile material into a bath of molten metal, whereby the volatile material helps to free copper from the metal melt.

Other objects and advantages will be obvious from the detailed description of the process appearing in the specification.

In the practice of this invention, the halide-containing compound is mixed with sulfur to form the treating agent, and the agent combined with the coppr-containing molten metal by (1) placing the agent in the bottom of the furnace or crucible prior to melting the metal; or (2) adding the agent to the molten metal; or (3) pouring the molten metal into a ladle containing the agent. When the agent contacts the molten metal, heavy fumes containing the copper are given off. After the fuming ceases, the molten mass can be cast or poured. An easily removable slag, which contains elements from the agent, forms on top of the resultant ingot. After slag removal, the ingot, substantially free of copper, can be worked in the conventional manner.

To obtain substantial removal of the copper, sulfur is preferably added in amounts ranging from about 2 to about 6 parts per part of copper; the halide-containing 3,441,404 Patented Apr. 29, 1969 ice compound being added in amounts ranging from about 4 to about 8 parts per part of sulfur. If lesser amounts of treating agent are employed, smaller percentages of copper will be removed.

The following examples illustrate the efi'ectivenss of the process of the present invention:

EXAMPLE I Cast iron, copper and the treating agent were used in the following percentages:

Grams Cast iron 45 Copper metal 5 K SiF 30 Sulfur 10 The potassium silicofluoride and sulfur were placed in the bottom of a graphite crucible; the cast iron mixed with the copper was placed on top of the treating agent. The crucible was then placed in a furnace and the mixture melted. Once fuming had ceased, the melt was removed from the furnace and a button was cast.

Results.0n cooling, the slag was removed from the metal button which was cut into sections, and the shavings were analyzed. The analysis gave the following results:

Percent K 0 Ca 0 Ti .1 V 0 Cr .3 Fe Major constituen Ni .1 Cu .2

These data indicates that 98 percent of the copper was removed from the metal melt during the process.

EXAMPLE II Grams Sulfur used none Cast iron 45 Copper metal 5 K SiF 30 The object was to test only potassium silicofluoride as a treating agent. The materials were treated and processed as in Example I. After melting and cooling was completed, the sample was prepared for analysis.

Results.Spectrographic analysis showed that only 50 percent of the copper was removed by this method, pointing up the fact that sulfur is an important component of the process.

EXAMPLE III In this example only sulfur was used as a treating agent. Grams Cast iron 45 Copper metal 5 Sulfur 30 3 in combination, larger amounts of these agents remove greater amounts of copper.

Besides the fluorides, other halides such as alkali and alkali earth metal chlorides and bromides are effective copper removal agents.

Copper can substantially be removed by the process of the present invention from ferrous metals such as scrap iron and alloy steels containing up to as much as about 30% copper by weight. Furthermore, by the process, junked cars which present a disposal problem and even larger stockpiles of other scrap metal would be available for reprocessing. Any of the furnacing techniques now used by the industry could be employed. Finally, the removed copper composition could be recovered by, for example, filtering or washing the gas or fumes, or by any other conventional method.

Although the particular process herein described is well adapted to carry out the objects of the present invention, it is to be understood that various modifications and changes may be made all coming within the scope of the following claims.

What is claimed is:

1. A process for removing copper from a copper-com taining ferrous metal comprising reacting the said coppercontaining ferrous metal while in a molten state with sulfur and a halide-containing compound selected from the group consisting of alkali metal halides, alkali earth metal halides, alkali metal silicohalides, alkali earth metal silicohalides, KMgF KAlF K TiF K ZrF and K SnF to strip said copper from said copper-containing ferrous metal.

2. The process of claim 1 wherein said halide-containing compound is a fluoride-containing compound.

3. The process of claim 1 wherein said halide-containing compound is potassium silicofluoride.

4. The process of claim 1 wherein said reaction step comprises mixing said molten metal with sulfur and said halide-containing compound.

5. The process of claim 4 wherein said halide-containing compound is a fluoride.

6. The process of claim 4 wherein said halide-containing compound is potassium silicofluoride.

7. The process of claim 4 wherein said metal contains less than about 30% by weight copper, and wherein said 0 sulfur is added in an amount ranging from about 2 to about 6 parts per part of copper present in said metal, and said halide-containing compound is added in an amount ranging from about 4 to about 8 parts per part of sulfur added.

8. The process of claim 1 wherein said metal is scrap irOn.

9. The process of claim 2 wherein said metal is scrap iron.

10. The process of claim 3 wherein said metal is scrap iron.

References Cited UNITED STATES PATENTS 393,258 Beck 1l0-85 2,362,202 11/1944 Hay 23l35 X 2,403,419 7/1946 Wilkins 75-44 2,662,009 12/1953 Roberts 75108 2,683,085 7/1954 Lohberg 75-63 L. DEWAYNE RUTLEDGE, Primary Examiner.

J. E. LEGRU, Assistant Examiner.

US. Cl. X.R. 

